Thanks, interesting responses. I don't think my problem is with the tactics themselves; they might have a place in a well-balanced game; it's just that they're so good that they're nearly automatic. Virtually every other Civic is a decision; Police State, Bureaucracy, Pacifism, etc. But Slavery is so good it's a no-brainer, and some players don't give it up until relatively late in the game, if at all. There are admittedly a few other Civics that are no-brainers like Hereditary Rule, but they aren't the dramatic game-changers that Slavery is.
I've been tweaking the yields a bit trying to find a good balance. One thing I've tried is reducing the food output of grasslands and increasing that of Forests. After all, unless you're a cow, how is uncultivated grassland going to provide more food than a forest? Forests have big trees and lots of animals precisely because their location can support more life. However, I found that the +1 Food for Forests discouraged building improvements which reduced the usefulness of Workers, so I haven't quite figured out a solution there.
Adjusting the yields of the tile and/or of the chop is certainly worth considering; and lowering the yields for earlier tech levels has helped limit the chopping somewhat. I'm not sure what the solution is; it's possible to go the other way, and make forest so good that nobody ever cuts it down and instead goes with nothing but forest (Alpha Centauri all over again!) I like the option of clearing forest; I'm just hesitant about the prospect of rewarding the nearby city with a boatload of easy hammers for it.
I agree that whipping seems too popular (and powerful). I think that the best way to deal with this though is simply to increase the penalties for whipping and running Slavery at all. Increased slave revolts could be one option. Making bigger populations more valuable could be another. You could also make infantry and cavalry units use Food Production. That would place a somewhat higher premium on food and population.
Having military units use of food actually makes sense, but that would require a major rebalancing of the game. I do think that the production bonus makes sense for Slavery--the problem, though, is that the extra production comes up front, which makes it very tempting to use regularly, as it can dramatically speed up production. That's why I favor having it give a bonus over time--say, thirty hammers spread out over ten turns (the same ten turns of unhappiness) rather than all at once. Same effect, but not as much a temptation to use.
Yeah.. no one's
ever been forced into military service.
OK, point taken! Although slave armies (Mameluks excepted) do not exactly have a stellar track record; virtually all the dominant armies of history have consisted primarily of freemen (even Greek triremes, which were manned by Greek citizens, not slaves, with all apologies to "Ben Hur".)
Now that I think about it, though, one of the problems is that, other than slavery, there is no other way to rush military production in the early game. I wonder if the Draft button comes too late in the game--realistically (I know, this is not a hyper-realistic game, but it's still an argument) early societies had what we consider to be mass conscription to fill the ranks of their forces. I think I'd prefer to see the Draft button much earlier, although as I think it's a bit powerful, it might need to have an additional penalty attached (like in Civ3, where drafted units were "green" and more vulnerable.) Maybe then have Nationalism reduce the penalty on drafted units; that would help make Nationalism less of a no-brainer Civic pick as well.